I. Field of the Invention
The present invention relates generally to boring bars and, more particularly, to a boring bar in which the radial position of the cutting tool is adjustable.
II. Description of the Prior Art
There are a number of previously known boring bars and these boring bars are used in a plurality of different applications. In general, however, each boring bar includes an elongated body having one end adapted to be positioned within and held by a tool holder or chuck of a rotary drive machine. Thus, upon rotation of the machine, the boring bar body is rotatably driven about the axis.
A cutting tool or tool insert in turn is attached to the opposite end of the body of the boring bar. The cutting tool extends generally radially away from the axis of the boring bar body and has a cutting edge which performs the cutting operation on the work during a boring operation. In addition, there have been a number of previously known boring bars in which the radial position of the tool with respect to the longitudinal axis of the boring bar is adjustable which correspondingly varies the diameter of the hole which is bored. These previously known boring bars, however, all suffer from a number of common disadvantages.
One disadvantage of these previously known boring bars is that the cutting tool or tool insert must be specially fabricated for the particularly boring bar. Thus, a boring bar constructed by one manufacturer will only accept cutting tools or tool inserts purchased from one, and usually the same, manufacturer. Moreover, these cutting tools and tool inserts are very expensive and expense of the cutting tools and tool inserts is further aggrevated since the required tool or insert is available from only a single source.
A still further disadvantage of these previously known boring bars is that the mechanism for adjusting the radial position of the cutting tool have not been wholly satisfactory in use. One problem of these previously known adjustable boring bars is that the cutting tool can only be accurately adjusted to within a thousand of an inch, more or less, of the desired diameter to be bored. In many high precision boring operations, however, a boring accuracy to within a ten thousand of an inch, more or less, is required. In order to obtain such high precision, special boring bars must then be used.
A still further disadvantage of these previously known boring bars is that the range diameters which a single boring bar can cut is also very limited, oftentimes to within a fraction of an inch. Thus, in order to be able to bore holes of fixed diameters over a relatively wide range, for example, several inches, it has been heretofore necessary for machine shops and the like to maintain a plurality of different boring bars in stock wherein each boring bar is capable of boring holes in a different diameter range. This solution, however, is undesirable in view of the high cost of both the boring bar and their cutting tools or tool inserts.